Machines for removing roadway surface for replacement or repair often make use of a rotating cylinder ("mandrel") having spiral flights along the peripheral surface. A plurality of teeth or bits are mounted to the flights by replaceable brackets for engaging and cutting through the roadway surface as the mandrel rotates. The teeth are typically removable from the brackets. The brackets, in turn, may be removed from the mandrel flights for replacement.
Efforts have been made to extend the useful life of the cutter teeth. Probably the most significant advance has been development of teeth with cylindrical shanks mounted in brackets with lock sleeves that allow the teeth to rotate. A freely rotatable tooth will not constantly expose a single surface to wear. Instead, the tooth will wear evenly about its periphery.
Even with the above advancements, the cutting teeth must be replaced quite frequently. It is not unusual to replace a full set of teeth twice in a single nine-hour work shift. This wear is expected and accepted as unavoidable since the teeth are the elements used directly against the roadway surface for material break-up and removal.
Much attention has been given the cutter teeth due to the extreme wear factor and required frequency of replacement. But the brackets that mount the teeth also wear significantly. Consequently, they must be replaced periodically, though not nearly as frequently as the teeth. Brackets generally require replacement after about sixty work days.
Replacement of brackets, unlike tooth replacement, requires substantially more "down time" for the equipment. It is a time-consuming, labor-intensive chore to remove and replace brackets, especially those that have been welded in place. The per-unit cost of bracket replacement, including labor, is substantially more than the cost of wear teeth and labor for their replacement on the brackets. It therefore becomes desirable to acquire some form of protection for the brackets that will extend their useful life and consequently reduce the amount of "down time" and operating costs.